Logical Reasoning

PT137 · S3 · Q11 A mass of

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A mass of "black water" containing noxious organic material swept through Laurel Bay last year.

Conclusion

At no point in the past two centuries, has black water been intense as it was last year.

Evidence

The black water wiped out five species of coral, including some that were more than two centuries old.

Evaluation

If this round of black water killed 200+ year old coral, does that mean that it was the strongest round of black water in the last 200 years?

The author is thinking,

To find the wiggle room, we would need to solve this riddle: if a previous wave of black water was stronger than last year's wave, how could it be that the previous wave didn't wipe out this old coral, but last year's wave did?

Maybe that (hypothetical) stronger previous wave just entered at a different angle, so it didn't impact the coral the same way. Maybe it "loosened the lid on the jar" and the second wave finished off the job. Maybe weather differences contributed to how the black water interacted with that coral (strong winds kept previous masses of black water from doing as much damage?)

Goal

The correct answer should either name the author's connective bridge, , or the correct answer will rule out an objection that allows one to argue that a previous, stronger wave might have occurred but just not wiped out the coral for some reason.

11.

Which one of the following is an assumption required by the argument?

  1. Masses of black water such

    Author Was Noncommittal

    The author allowed for the possibility that black water has come in the past two centuries, but she never committed to the idea that it has. So our author's argument is indifferent to the frequency at which black water comes. The author/argument only cares whether the episode of black water from a year ago was the most intense one of the past 200 years.

    8% picked this

  2. Every species of coral in

    Too Strong: every

    The author claimed that five species were wiped out. We don't know whether or not every species was harmed. We know at least five were. The author's argument doesn't hinge on 100% of coral being harmed. It is leaning purely on the idea that "if you wiped out coral that was more than 200 years old, then you're the strongest thing that has happened in the last 200 years".

    3% picked this

  3. The mass of black water

    Too Strong

    Too Strong: "any" Out of Scope: "species that use coral" Opposite This is too strong. The author doesn't need to assume that the black water didn't decimate other stuff too. Not to mention, if we negate this and say that the black water also decimated stuff that makes use of coral, it would only make the black water seem more damaging / more intense, and thus it would just strengthen the author's conclusion.

    2% picked this

  4. Correct

    The mounds of centuries-old coral

    Why this is right

    If we negate this, we get a powerful objection that "the 200 year old coral was in an especially fragile condition just before the black water swept in". This suggests that last year's black water wasn't the strongest in two centuries, it was just the straw that broke the camel's back. Maybe a previous round of black water (or something else) had pummeled the coral so bad that the coral was almost wiped out, but barely held on. When we see an answer choice with "ruling out" language on Necessary Assumption, we should negate it (by removing the "not") to see if it becomes an objection.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    84% picked this

  5. Older specimens of coral in

    Opposite

    It wouldn't help the author if the older specimens were weaker / more vulnerable. The author is interpreting the wiping out of the older specimen (200+ years) as her primary evidence that this black water was the strongest in 200 years. If the older specimens were more vulnerable, then it's less impressive that last year's black water wiped out an older specimen.

    3% picked this

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